Calculating Exposure
=======================

This section explains how to calculate exposure in the RiskChanges platform, based on the hazard and element-at-risk (EaR) data previously uploaded. Users can choose to compute exposure either for individual features or aggregated by administrative boundaries.

Overview 
^^^^^^^^^^^
Calculation identifies which elements are affected by a hazard based on spatial overlap. The output includes both spatial layers and attribute tables with key indicators. 

There are two modes of calculation:

- **Individual:** calculates at the feature level (e.g., per building or road segment).
- **Aggregated:** calculates exposure based on administrative units (e.g., parish level).

**Note:** The aggregated calculation requires a calculated individual exposure layer to be available.


Instructions
^^^^^^^^^^^^^^^

1. **Open the Exposure Module**
   
   - Go to the **Project Page**.
   - Click on the **Exposure** tab ni the sidebar.
   - Click **Add Exposure** to begin.

2. **Select Calculation Type**
   
   You will see two tabs:
   - **Individual:** for feature-level exposure results.
   - **Aggregated:** for summarized results by administrative boundaries. 

3. **Fill in General Information**
   
   In the **General** section, enter the following:
   - **Layer Name:** name for the exposure result layer.
   - **Hazard Layer:** select a previously uploaded hazard dataset.
   - **Elements-at-Risk Layer:** select the EaR dataset to be assessed.
   - **Intensity type:** choose from: *Minimum, Average,* or *Maximum*.
  
  Note: This setting controls the map visualization after the calculation. All intensity types will still be calculated in the background and can be switched later.

4. **Run the Calculation**
   
   - Click **Save** to start the exposure calculation.
   - Once completed, the platform will display the result on the map.

.. figure:: /images/tutorials_exposure/exposurepage.png
   :scale: 60%
   :align: center

   *Calculate exposure settings*

Results and Output
^^^^^^^^^^^^^^^^^^^^^
The exposure calculation produces:

* A spatial map layer showing the exposed features or areas.
* A table dispplaying detailed exposure statistics, including:

   - Minimum, average, and maximum hazard intensity affecting each feature.
   - Exposed area, length, or fraction.

Users can inspect and download this data or use it in further modules.

.. figure:: /images/tutorials_exposure/resulttable.png
   :scale: 60%
   :align: center

   *Exposure calculation result in a table*

There is also a feature summary table that provides an overview of the exposure results. This feature provides both table and chart views for better understanding.

.. figure:: /images/tutorials_exposure/resultsummary.png
   :scale: 60%
   :align: center

   *Exposure calculation result summary*

.. figure:: /images/tutorials_exposure/resultchart.png
   :scale: 60%
   :align: center

   *Exposure calculation summary in a chart*

Map Visualization
^^^^^^^^^^^^^^^^^^^^
Once exposure is calculated, the results appear on the **Map Panel** on the right side of the screen.

**Map tools include:**

* Zoom In / Zoom Out
* Reset to North
* Reset Map View
* Full-screen Mode
* Center on Current Location
* Layer Options (for switching basemaps: OpenStreetMap or Satellite)

.. figure:: /images/tutorials_exposure/mapdisplay.png
   :scale: 60%
   :align: center

   *Map display in RiskChanges*

**Legend and Layer Settings:**

* When a layer is selected, users can:
  - Reorder layers (drag and drop)
  - Zoom to layer
  - Adjust opacity
  - Toggle visibility
  - Show / hide legend
  - Remove layer

Users can also *click on features* on the map to view attribute data such as exposure levels, number of floors, or intensity values.

.. figure:: /images/tutorials_exposure/resultmapzoom.png
   :scale: 60%
   :align: center

   *Focusing on one feature to see the result details*

Filter and Style the Results
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

* Users can choose which *intensity type* (min/avg/max) to show on the map.
* Style and symbology xan be adjusted to better visualize the data. 
* Specific *classes or ranges* can be selected for focused viewing. The map will filter accordingly.

.. figure:: /images/tutorials_exposure/resultmap.png
   :scale: 60%
   :align: center

   *Exposure result map visualization*

Download the Map
^^^^^^^^^^^^^^^^^^^
The **Download** button allows users to export a map layout:

* **Default Setting:** a pre-formatted layout is downloaded automatically.
* **Custom Setting:** users can define:

   - Page Type or Resolution
   - Orientation (portrait or landscape)
   - Output format (e.g., PNG, PDF)

.. figure:: /images/tutorials_exposure/downloadmap.png
   :scale: 60%
   :align: center

   *Download map feature*